Diazinon was produced for the first time by Glysin and Margot by reacting 2-isopropyl-4-methyl-6-hydroxy-pyrimidine (hereinafter hydroxypyrimidine) with diethyl-thiophosphoryl chloride (hereinafter TPC) in an inert solvent, in the presence of potassium carbonate as described in United Kingdom patent number 713.278.
In this heterogeneous reaction the potassium pyrimidinolate is initially formed by heating the hydroxypyrimidine with potassium carbonate in benzene, with simultaneous removal of the water formed. The potassium salt so produced is then reacted with TPC by heating for several hours, the potassium chloride formed extracted by washing with water, and the solvent removed under reduced pressure.
The standard process for the industrial manufacture of diazinon is carried out essentially by means of a 4-stage synthesis, as described in great detail in U.S. Pat. No. 5,231,180; whose contents are incorporated by its reference herein.
The novel process described in U.S. Pat. No. 5,231,180 involves the reaction of the hydroxypyrimidine with TPC by first mixing the hydroxyprimidine with a select group of organic solvents, removing water by azeotropic distillation, adding dry potassium carbonate in a mole ratio of carbonate to hydroxypyrimidine of 1:1 to 1.2:1, and adding less than a stoichiometric amount of TPC to for the diazinon.
While this process afformed fairly pure diazinon, the use of excess potassium carbonate is expensive and a cause for concern in its removal from the waste water.